The change in the color of keratinic fibers, especially of hair, represents an important area of modern cosmetics. In this way, the appearance of the hair can be adapted to current fashion currents as well as to the individual desires of the particular person. Someone of ordinary skill in the art knows various possibilities for changing the color of hair.
The color of hair can be changed temporally by using substantive dyes. In this case, ready-made dyes diffuse from the colorant, which has already been produced, into the hair fiber. The dyeing with substantive dyes is associated with slight hair damage. However, a disadvantage is the low durability and the rapid leaching of the dyeings obtained with substantive dyes.
If the consumer wants a long lasting color result or a shade, which is lighter than his initial hair color, oxidative color changing agents are usually used. So-called oxidation dyes are used for permanent, intensive dyeings with corresponding genuiness properties. Such dyes usually contain oxidation dye precursors, so-called developer components and coupler components, which form the actual dyes under the influence of oxidizing agents—generally hydrogen peroxide. Oxidation dyes are distinguished by outstanding, long-lasting dyeing results.
Oxidative color-changing agents usually are marketed in the form of two-component compositions, in which two different preparations are present separately in two separate containers and have to be mixed with one another shortly before use.
The first preparation is a formulation, which is usually made acidic for reasons of stability and which contains hydrogen peroxide as an oxidizing agent in concentrations of 1 to 12% by weight. The oxidizing agent usually is formulated as an emulsion or dispersion and generally is made available in a plastic bottle with a reclosable outlet opening (developer bottle).
The second preparation is an alkaline formulation, which is often in the form of a cream or a gel and which additionally also contains the precursors of the oxidation dye if, at the same time with the brightening, a color change is also desired. This second component is provided in most cases in a tube, more rarely in a plastic container or in a glass bottle.
To prepare the ready-for-use mixture, the consumer must mix the two preparations with one another shortly before use. For this purpose, the alkaline cream or gel component is usually transferred completely from the tube or the glass or plastic container into the developer bottle, the two components are then mixed together as completely and homogeneously as possible by shaking and finally removed through an outlet opening in the head of the developer bottle.
However, this separate mixing process has a series of disadvantages for the user. Thus, the incomplete emptying of the tube can alter the quantitative ratio of the two components, which leads to deviations in the desired coloring result. If the two components are not shaken or mixed long enough, the application mixture is inhomogeneous with the result that a non-uniform color results. In addition, it is also desirable for reasons of user comfort to dispense with this mixing step completely.
In order to avoid these disadvantages, multi-chamber containers with a common dispenser opening were developed, in which the two components are mixed in the valve or dispenser during the exit. Removal of the application mixture through the dispenser makes mixing of the components by the user superfluous and has increased the application comfort significantly.
In an embodiment, which is particularly convenient for the user, the multi-chamber container with a common dispensing opening is an aerosol product. As a result of the propellant present in the aerosol product, the two preparations can be removed uniformly in the form of a homogeneous foam if the user exerts pressure on the valve or the dispenser. Since the two preparations are mixed in the valve or dispenser during removal, mixing, shaking or stirring by the user, which is associated with effort, is no longer required.
The outer wall of very many aerosol containers includes metal. The two preparations, which are to be mixed at the beginning of the oxidative color changing process, contain very reactive chemicals with strong alkalizing agents and oxidizing agents and have special requirements for storage and packaging in the aerosol system. In order to avoid unwanted side reactions (such as the corrosion of the metal aerosol container), these two preparations are therefore not filled directly into two chambers of an aerosol container, but are initially filled into two separate pouches, which are inside the metal aerosol container.
For removing the two preparations out of the pouches, two tubes, which are connected with the valve, protrude into each pouch. When the valve is actuated, the preparations are then pressed by the propellant gas from each pouch through the two pipes in the direction of the valve, mixed with one another just below or just above the valve, and then emerge from the valve in the form of the application mixture.
The exact construction of these two-chamber aerosol systems, which are provided with pouches, is disclosed, for example, in EP 2009/0108021 A1 or in US patent 2009/0108021 A1, to the contents of which reference is made here.
In order to prevent escape of the contents (particularly of the reactive agents) from the pouches, the latter usually includes at least two layers, an inner polymer layer and an outer metal layer (such as, for example, aluminum). The outer metal or aluminum layer is highly impermeable to gases and prevents the escape of oxygen (caused by the decomposition of hydrogen peroxide), the evaporation of water or ammonia, and also the escape of all other volatile constituents, such as, for example, solvents.
In order to prevent direct contact between the preparations and the metal or aluminum foil, at least one additional polymer layer is applied to the aluminum layers on the inside of the pouches. This inner polymer layer is, for example, a layer of a synthetic polyolefin polymer. These two layers may also be connected to one another by an adhesive layer, which may include an adhesive polymer. In this case, the pouches comprise at least three layers: an inner layer of a synthetic polyolefin polymer, a middle layer of an adhesive polymer and an outer layer of an aluminum foil.
For lining or protecting the outer metal or aluminum layer further, the latter may also be coated with a further polymer layer on the outside. In this case, the pouches comprise at least four layers: an inner layer of a synthetic polyolefin polymer, a middle layer of an adhesive polymer and an outer layer of an aluminum foil and, on the very outside, once more a layer of a synthetic polyolefin polymer.
A general disadvantage of this pouch structure is that the two layers of an inner (polyolefin) polymer and, if appropriate, an intermediate adhesive polymer, cannot completely prevent the penetration of the hydrogen peroxide up to the aluminum foil. If the hydrogen peroxide then undesirably diffuses through both polymer layers, hydrogen peroxide and aluminum can react with one another, which can lead to the decomposition of hydrogen peroxide, to the formation of oxygen and to the inflation of the pouch. Because of these side reactions, the shelf life of the hydrogen peroxide-containing preparations in the aforementioned pouches is greatly reduced.